Distribution of adrenomedullin-like immunoreactivity in the central nervous system of the frog

Adrenomedullin (AM) is a recently discovered peptide widely distributed in the mammalian brain. By using an antiserum specific for human AM, we have a nalyzed the localization of AM-like immunoreactivity in the brain and spina l cord of the anuran amphibian Rana perezi. Cell bodies immunoreactive (AMi ) for AM were located in the dorsal, lateral and medial pallial regions, di agonal band of Broca, medial septum, and above and rostral to the anterior commissure. A large population of AMi neurons was located in the anterior p reoptic area, suprachiasmatic nucleus and in the infundibular hypothalamus. The processes of these latter cells are part of the hypothalamo-hypophysia l pathway to the neural and intermediate lobes. Labeled cells were observed in the pretectal region, posterior tubercle and the mesencephalic anterove ntral tegmental nucleus. Strikingly, Purkinje cells in the cerebellum also showed AM immunoreactivity. albeit not all of these cells were equally stai ned. Additional cells M ere located in the parabrachial region, principal t rigeminal sensory nucleus, reticular nuclei medius and inferior, and the in termediolateral gray of the spinal cord. Immunolabeled fibers were widespre ad throughout the brain and spinal cord of the frog. They were particularly abundant in the medial amygdala, hypothalamus, mesencephalic tectum, periv entricular pray and spinal cord. The distribution pattern of AM-like immuno reactivity in the brain of the frog is very selective and does not correspo nd with the pattern observed for any other transmitter or neuroactive molec ule. The wide distribution of this peptide strongly suggests that it may pl ay a significant role in the multiple neuronal functions in the amphibian b rain. (C) 2001 Elsevier Science B.V. All rights reserved.